This application relates to DNAs, isolated from banana (Musa), DNA constructs containing the banana DNA, plant cells containing the constructs and plants derived therefrom. In particular it involves the use of antisense or sense RNA technology to control gene expression in plants.
Many physiological and developmental processes are controlled by ethylene in higher plants, including banana (Genus: Musa). These processes include fruit ripening where ethylene may be involved in both the initiation and rate of continuation of many of the changes involved in fruit ripening. However the exact role of ethylene has hitherto not been fully understood. We have now isolated a DNA involved in the generation of ethylene in bananas. In this invention, we provide such DNA, and methods of using it. One such use is a method for controlling the rate of production of ethylene in ripening bananas. In this way the rate of many of the ethylene-related changes associated with fruit ripening on a plant can be modified to obtain desired ripening characteristics.
The modification of plant gene expression has been achieved by several methods. The molecular biologist can choose from a range of known methods to decrease or increase gene expression or to alter the spatial or temporal expression of a particular gene. For example, the expression of either specific antisense RNA or partial (truncated) sense RNA has been utilised to reduce the expression of various target genes in plants (as reviewed by Bird and Ray, 1991, Biotechnology and Genetic Engineering Reviews 9:207-227). These techniques involve the incorporation into the genome of the plant of a synthetic gene designed to express either antisense or sense RNA. They have been successfully used to down-regulate the expression of a range of individual genes involved in the development and ripening of tomato fruit (Gray et al, 1992, Plant Molecular Biology, 19:69-87). Methods to increase the expression of a target gene have also been developed. For example, additional genes designed to express RNA containing the complete coding region of the target gene may be incorporated into the genome of the plant to "over-express" the gene product. Various other methods to modify gene expression are known; for example, the use of alternative regulatory sequences.
An object of the present invention is to provide new materials for use in the genetic control of ethylene biosynthesis in fruit, and hence ethylene-induced processes involved in fruit ripening, particularly banana fruit.